lipids & nucleic acids
DESCRIPTION
Lipids & Nucleic Acids. Lipids: Basic Information. Lipids are defined as groups of molecules that are insoluble in water. Fats (triglycerides), oils, waxes, and steroids. Long chains of CH 2 units Molecules are nonpolar. Phospholipids. Special types of lipid - PowerPoint PPT PresentationTRANSCRIPT
Lipids & Nucleic Acids
Lipids: Basic Information• Lipids are defined as
groups of molecules that are insoluble in water.
– Fats (triglycerides), oils, waxes, and steroids.
– Long chains of CH2 units
–Molecules are nonpolar
Phospholipids
• Special types of lipid• form the core of all biological
membranes.
Types of LipidsType Organismal Use Human Uses
Fats Long-term energy storage & thermal insulation in animals
Butter lard
Oils Long-term energy storage in plants and their seeds
Cooking oils
Phospholipids Component of plasma membrane No-stick pan spray
Steroids Component of plasma membrane; hormones
Medicines
Waxes Wear resistance; retain water polishes
Lipids are hydrophobic• Lipids repel
water.• Ex. The cuticle of
plants is waxy. The waxy covering makes the plant water proof and minimizes water loss.
Building Blocks of Lipids• One glycerol-alcohol• Three fatty acid chains
Fats and Oils (triglycerides)
• Fats and oils consist of a glycerol molecule with three attached fatty acids (triglyceride / triglycerol).– Saturated fats - all internal carbon atoms are
bonded to at least two hydrogen atoms–usually a solid at room temperature
– Unsaturated fats - at least one double bond between successive carbon atoms• Polyunsaturated - contains more than one
double bond–usually liquid at room
temperature
Fats as Energy Storage Molecules
• Fats, on average, yield about 9 kcal per gram versus 4 kcal per gram for carbohydrates.– Animal fats are saturated while most plant
fats are unsaturated.• Consumption of excess carbohydrates leads to
conversion into starch, glycogen, or fats for future use.
Triglycerides
Saturated vs. unsaturated fatty acids
Which fats are best?
• Unsaturated with one double bond can help lower cholestrol• Examples-olive and canola
• Saturated or hydrogenated are considered unhealthy and should be consumed in limited quanities
Cis and Trans
Hydrogenated Fats
• Hydrogenation is used to add hydrogens to unsaturated fats and make them more solid. If a fat is FULLY saturated, it becomes solid, like candle wax. If it is PARTIALLY saturated (the same as partially hydrogenated) the result is a semi-solid, like margarine.
Steroids• Steroid hormones are crucial substances for
the proper function of the body. They mediate a wide variety of vital physiological functions ranging from anti-inflammatory agents to regulating events during pregnancy.
• They are synthesized and secreted into the bloodstream by endocrine glands such as the adrenal cortex and the gonads (ovary and testis).
• Skeleton made of four fused carbon rings• Cholesterol is a steroid
as well as the foundation for other steroids.
Waxes Long-chain fatty acid
bonded to a long-chain alcohol
• High melting point
• Waterproof
• Resistant to degradation
• Why do you wax a car?
Waxes
Phospholipids
Phospholipids• Derived from triglycerides
– Glycerol backbone– Two fatty acids attached instead of three– Third fatty acid replaced by phosphate group
• The fatty acids are nonpolar and hydrophobic• The phosphate group is polar and hydrophilic
• Molecules self arrange when placed in water
– Polar phosphate “heads” next to water
– Nonpolar fatty acid tails” overlap and exclude water
– Spontaneously form double layer & a sphere
Phospholipid Structure• Phospholipid
molecules have one end which is attracted to water while the other is repelled by it. The fatty acid end is not attracted to water and is called hydrophobic. At the other end of the molecule the phosphate group is attracted to water, it is said to be hydrophilic.
Hydrophobic Tail
Hydrophilic Head
Phospholipids Form Membranes
Nucleic Acids
Nucleic Acids
• Deoxyribonucleic Acid (DNA)– Encodes information used to assemble
proteins.• Ribonucleic Acid (RNA)– Reads DNA-encoded information to
direct protein synthesis.
Adenosine triphosphate (ATP)– Provides energy
Nucleic Acid Structure• Nucleic acids are composed of long
polymers of repeating subunits, nucleotides - the monomer.– five-carbon sugar– phosphate– nitrogenous base• purines
– adenine and guanine
• pyrimidines– cytosine, thymine, and uracil
Nucleic Acid Structure
• DNA exists as double-stranded molecules.– Genetic info. - coded for by the order of
the nucleotides.– double helix– complementary base pairing• hydrogen bonding • base pairing: A-T, C-G
• RNA exists as a single stand.– contains ribose instead of deoxyribose– contains uracil in place of thymine
Nucleotides
•No•Yes•Helix•Interprets genetic info; protein synthesis•Heredity; cellular control center•Function•Cell nucleus and cytoplasm•Chromosomes of cell nucleus•Where
Comparison of DNA & RNA
•Mostly single stranded•Double-stranded; Pairing across strands•Strands
•Cytosine, guanine;•adenine, uracil
•Cytosine, guanine;adenine, thymine•Bases
•Ribose•Deoxyribose•Sugar
•RNA•DNA•Feature
Structure of DNA
RNA Structure
DNA RNA Protein
Other Nucleic Acids
• ATP (adenosine triphosphate) is composed of adenine, ribose, and three phosphates
• In cells, one phosphate bond is hydrolyzed – Yields:
– The molecule ADP (adenosine diphosphate)
– An inorganic phosphate molecule pi
– Energy
• Other energy sources used to put ADP and pi back together again
ATP